Geometric sequence :
#a_1= (x+3) , a_2= (-2x^2-6x) = -2x(x+3)= -2x*a_1#
# a_3= 4x^3+12x^2 = -2x(-2x^2-6x) = -2x* a_2#
First term is #a_1= (x+3)# and common ratio is # r= -2x#
#n# th term of G.P is # a_n= a_1*r^(n-1)#
#:. 8# th term of the sequence is # a_8= a_1*(-2x)^(8-1)# or
# a_8= (x+3)*(-2x)^(8-1) or a_8= (x+3)*(-2x)^7 # or
# a_8= (x+3)*(-128x^7) or a_8= -128x^7(x+3) # or
#a_8= -128x^8 -384x^7 #
#:. 8# th term of the sequence is #-128x^8 -384x^7 # [Ans]